U.S. Pat. No. 4,217,377 describes a crosslinking agent for powder coatings which is a low molecular weight adduct of a monohydroxy, single ring aromatic carbon compound and a hexakis (alkoxymethyl) amino-triazine. The products described in U.S. Pat. No. 4,217,377 retain two of the six theoritical methoxy group of the triazine during the preparation, as the methoxy groups are the crosslinking groups of the adduct.
A novel polyhydric, polynuclear phenol-melamine adduct has now been found which is an effective crosslinking agent for epoxy resins and which contain no methoxy groups. As noted, the adducts of U.S. Pat. No. 4,217,377 contain unreacted methoxy groups. The present adducts, on the other hand, are prepared by reacting the phenol with the triazine so that the ratio of phenolic OH groups to methylol groups is at least 2:1, all methylol groups are thus reacted, to produce a phenolic-terminated oligomer which will cure via etherification with the epoxy groups of the epoxy resin. Thus, the present novel adducts provide melamine resin type properties in the cured film without evolving methanol thereby essentially preventing void formation due to emission of volatiles during cure. This is particularly important in rapid curing, thick (.about.10-20 mil) castings where void formation can be a problem.